Windows 10 Technical Preview for Phones is a very early release. According to Microsoft General Manager Gabe Aul, it is the earliest build of a mobile OS we've seen from the company. Usually only internal engineering folks get to see OS builds this early.

But this build is more about aligning the underlying operating system code with the desktop version of Windows 10. Because of that, what the end user sees is on the rough side. Not only are new features unfinished, but even some features that work well in Windows Phone 8.1 are missing or less functional.

How to Get Windows 10 Technical Preview for Phones Most people probably shouldn't install this software; it's definitely not for a primary or essential phone. But if your curiosity about things like new mobile operating systems is simply unquenchable, you can get the preview by joining the Windows Insider Program. And you can only install it on a few select Lumia models of Windows Phone hardware—the 630, 638, 635, 730, 636, and 830. Most carriers are supported, and more models will be added as new previews are released. The build is available in 25 languages, though not all interface elements have been translated. Fortunately, there's a rollback capability if you want to restore the phone to a stable OS version.

Getting the new OS involves downloading and installing the Windows Insider app. When you run the app, you'll tap Get Preview Builds, and then have a choice between Insider Slow and Insider Fast. As you may guess, the former come later but are more likely to be stable. If you choose Insider Fast, you'll see new features sooner, but you're more likely to be left in the lurch if a bug shows up.

Once you've made that choice, be prepared for a very long installation process. On my test Lumia 830 the whole process (via Insider Fast) took 3 hours and 46 minutes, with long download sessions and a couple of reboots along the way. Do note that the Wi-Fi connection used for this process wasn't the fastest around, so you may finish faster.

New Design, New Features At a glance, the lock and home screens look nearly identical with Windows Phone 8.1. But just tap into Settings, and you can see a new look, with the line-drawing style icons we saw in Windows 10 Technical Preview for PCs. It looks fine, but it's a departure from the distinctive Windows Phone look with huge fonts for top-level menus. I'd love to see the ability to search for settings, though, as you can on Windows PCs.

A very evident and very welcome change shows up when you swipe down from the top of the screen to reveal notifications. At first, you'll see the same four quick-action tiles, but now there's an Expand down arrow to get you up to eight more options. I'm only sorry that flashlight isn't an option, as it is on iOS. When an email or Facebook message came in, the notification at the top of the screen was more flexible, but I couldn't integrate Skype into the messaging app yet, and I couldn't actually respond within the notification. This should work for SMS messages, but my test Lumia 830 didn't have cell service.

Another huge improvement is that you can now enter text with your voice anywhere a text box is waiting for your input. This actually adds up to a win over iOS, since you can use Windows Phone's excellent gesture-writing keyboard or voice input without having to change keyboards. And the voice-recognintion's language intelligence did understand the difference between "too" and "2" when I told it "I want pizza too" and "I want pizza at 2."

One new setting concerns the home-screen background. Though the official Windows blog says that using your own full-size image is new, you can already do that in Windows Phone 8.1. What is new is that instead of being completely transparent, the stock app tiles now use a tint based on your background. And in Windows 10, the background doesn't scroll up, but remains still. I'm not sure this is a big improvement, though the tinting is cool.

While unification of the Windows app store between PCs and mobile is a major goal of Windows 10, the phone preview store looks identical with that in Windows 8.1. I did have more problems with it, however: Even an attempt to install Microsoft's own Skype app resulted in an error message on the first try. One tweak for newly installed apps is that they appear at the top of your all-apps page that you get to by swiping the home screen. This is a handy feature, which I've appreciated on Windows 8.1 on the desktop, and one not found in competitors such as iOS and Android.

Photos The built-in Photos app has gotten a face-lift. Instead of swiping through All, Albums, and Favorites as in Windows Phone 8.1, you get a more iOS-like Collection view that organizes photos by date. A drop-down menu offers Albums and Folders as optional views, though both of these result in a "Coming Soon" page. The photo viewer has a welcome option to just show one image if there are exact duplicates. And you can include photos from your OneDrive camera roll along with those stored on the phone's local memory.

As in Windows Phone 8.1, you can edit, share, or delete photos, but there's no longer a heart icon for favoriting them, unfortunately. Editing is even more limited than in the existing Windows Phone Photos app. The only actions are cropping and rotating. No auto-fix button shows up, though Microsoft says a more powerful auto-enhance is coming.

Performance Without question it's too early to say anything incontrovertibly definitive about performance. First, I'll just note that aside from Store issues, I didn't run into crashes. Considering all the dire warnings about pre-release instability, I found the OS remarkably stable. I also ran two benchmarks: AnTuTu, which tests processor, memory and graphics performance; and SunSpider, which tests the browsers' JavaScript performance. I compared results with the same phone running Windows Phone 8.1.

On the Sunspider JavaScript benchmark, Windows 10 Preview took 1216ms, compared with 1240ms under 8.1. So the browser clearly hasn't been sped up yet, as it will when Project Spartan bears fruit. On AnTuTu, Windows 10 Preview scored an overall 9898, compared with 12023 on Windows Phone 8.1. Clearly, this OS needs to undergo a bit of optimization.

What's Not Ready? Cortana for One As is the case with the Windows 10 desktop technical preview, Cortana takes a step back compared with how she works in Windows 8.1 in this release. I couldn't open apps or initiate Skype calls, but setting reminders and checking the weather worked, and the Notebook, Places, and Quiet Hours options were present. Most requests resulted in a Web search, just as on Windows 10 Technical Preview on the desktop.

Too Early It seems Microsoft wanted to enlist the public at large in order to have this operating system ready for its aggressive schedule of June RTM and early fall GA. It's obvious this is not the type of data that most people will want to run on their phones, but I was surprised at the small set of glitches I encountered in a half day of using it. But in terms of feature-set fullness, the preview really only gives us a glimpse of what to expect in the commercial release of Windows 10 for phones, coming next fall.

About the Author

Michael Muchmore is PC Magazine's lead analyst for software and web applications. A native New Yorker, he has at various times headed up PC Magazine's coverage of Web development, enterprise software, and display technologies. Michael cowrote one of the first overviews of web services for a general audience. Before that he worked on PC Magazine's S... See Full Bio

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